2025-08-22 ENVIRONMENT DEVELOPMENT AND SUSTAINABILITY 2025 null(卷), null(期), (null页)
Soils serve as the largest terrestrial carbon reservoir, and soil aggregates-being the fundamental units of soil structure-play a key role in stabilizing soil organic carbon (SOC), preserving organic matter, and mitigating atmospheric CO2 emissions. However, the impact of different land use types on soil aggregate distribution and SOC dynamics remains poorly understood in the dry temperate Himalayan region. This study investigated the distribution of soil aggregates and associated SOC under four land uses: apple orchards (AO), agroforestry systems (AF), farmlands (FL), and wastelands (WL), across three soil depths (0-20, 20-40, and 40-60 cm). Soil samples were fractionated by wet sieving into macro-aggregates (250-2000 mu m), micro-aggregates (53-250 mu m), and silt-clay fractions (< 53 mu m) and analyzed for SOC content. Results revealed that macro-aggregates dominated (> 50%) across all land uses, decreasing with depth. AO recorded the highest macro-aggregate proportion (57.08%), while FL had the highest micro-aggregates (28.44%), and AF showed the highest silt-clay content (19.49%). MWD and GMD were highest in AO across all depths, indicating better aggregate stability. SOC content and density were also highest under AO, with macro-aggregates contributing most to SOC in AO (42.52%), AF (37.54%), and FL (40.25%), while in WL, micro-aggregates contributed the most (34.94%). These findings highlight the ecological significance of apple-based systems in enhancing SOC sequestration and improving soil structural stability. Promoting tree-based systems like orchards and agroforestry may serve as effective strategies for soil conservation and climate mitigation in fragile Himalayan ecosystems.